Trouble with 1.18 Cave Biome Plants

Hi, I'm trying to make a mod revolving around an underground biome using the 2022.1 1.18 cave biome generation option. However, even if I set plants to high values, they don't want to spawn. For example, a growable reed-like plant is supposed to spawn only in the biome, and the spawn frequency is 18, patch size is 124, and can generate at any height (it is technically a CAVE plant) However, no matter how hard I check, I can't find many of the plants I added. The only thing that does spawn is my grass-like plant, and not the flower-like plants. Is there a fix for this so that plants aren't impossibly rare when generating in underground biomes?